This invention pertains to winders for winding, onto a roll, sheet materials such as paper, plastics, metal foil, composites, and the like. Such winders are used for winding up sheet materials after they are made, such as at the end of a paper making machine or at the end of a plastics film extrusion operation. They are also used to wind up sheet materials after other processing operations, such as the various converting operations which are commonly performed on sheet materials.
In conventional use, a winder is positioned at the end of the processing line, and is used to wind up the sheet material in roll form, typically on a pre-formed roll core. It is believed that the sheet material approaching the roll carries with it a boundary layer of air. As sheet material is wound onto the roll, the boundary layer air tends to stay with it, and may serve as a pseudo-pneumatic air foil layer between adjacent layers of sheet material in the roll. This air foil may contribute to loosening or shifting of the layers relative to each other, which may make the roll hard to handle, or may make it susceptible to shipping damage; or the useful and undamaged width may be reduced unacceptably.
It has been found desirable, in conventional practice, to apply pressure to the outside of the winding roll as it is being wound up, to force dissipation of the boundary layer, so that the layers in the roll will have substantial sheet-to-sheet contact, and thus stabilize relative to each other and reduce loosening or shifting of the layers. The typical method of applying pressure is by means of a rider roll which rides on the outside surface of the main winding roll.
Turret winders are especially desirable for use with essentially continuous high speed sheet material-producing operations. For example, paper making machines may produce paper at a rate of 3000 feet per minute, or more. When a roll on a winder is full, the paper making machine continues to produce paper while the full roll is being replaced by a new and empty roll with a core in place. Thus it is important that the incoming paper be transferred quickly to the new and empty roll. Turret winders have been found useful to meet these requirements. Where used with turret winders, rider rolls have been mounted on each of the turret arms between the winding roll axis and the main axis about which the turret rotates.
The rider roll is generally positioned on the winding roll in such a location that the sheet comes under the pressure of the rider roll at about the same time that the sheet enters the roll, which may be at its point of tangency with the roll. In such a case, the sheet material is tangent to both the winding roll and the rider roll at essentially the same points. As the roll fills with the sheet material, the angular point of contact between the rider roll and the winding roll changes somewhat, for example clockwise, while the point of tangency between the winding roll and the sheet material may change in the opposite direction, for example counterclockwise. This shift may, in some operations, allow some of the boundary layer air to remain between the incoming layer and the adjacent inner layer, where the pressure is applied by the rider roll at a point after the point of tangency between the roll and the sheet material.
A more serious problem occurs when the winding roll is full and is rotated about the turret axis, such as 180 degrees to bring an empty roll into position. During the rotation of the turret, the winding roll continues to wind. In the process of the rotation, the rider roll rotates with the turret arm to which it is mounted. On a conventional two roll turret, where rotation of about 180 degrees is normal, the rider roll remains at about the same relative position on the winding roll while the point of tangency of the incoming sheet shifts with the rotation of the winding roll--about 180 degrees. Thus, after rotation of the turret, the sheet material is not pressed against the winding roll until it has traversed a 180 degree arc on the winding roll.
Another affect of the turret rotation is that a rider roll which has been on top of the winding roll is then below the winding roll, and its gravitational weight is no longer contributing to the applied pressure, but is, rather, working against it. Thus, the effective pressure applied may change.
In some cases, it may be desirable to continue winding temporarily on the full roll after rotation of the turret, such as to give time to complete a set-up operation or to correct a mechanical defect.
Any sheet material so wound, with the rider roll thus out of position relative to the point of tangency of the incoming sheet with the roll, is highly subject to the aforementioned shifting and loosening as when no rider roll is used.
It would be desirable to provide a rider roll mechanism wherein the rider roll would remain at the point of tangency between the sheet and the winding roll throughout the winding cycle; or at least the rider roll would remain at the point where the sheet material enters the winding roll.
It is an object of this invention to provide a rider roll assembly which may be mounted on a winder, and which may be controlled to stay at the point of tangency during winding, and may revolve about the winding roll, such as for loading and unloading operations.
It is another object to provide a winding assembly, including a rider roll mounted on the assembly in such a way that the position of the rider roll, in angular relation to the winding roll, may be readily changed, or adjusted.
Another object of the invention is to provide a rider roll assembly which may be mounted on a winder, and which may be controlled to be at the point where the sheet material enters the winding roll.